US10139660B2 - Display device and manufacturing method thereof - Google Patents

Abstract

A novel foldable display device or an electronic device using the same, e.g., a portable information processor or a portable communication information device, is provided. A foldable display device of which a display panel can be folded n times (n≥1, and n is a natural number) at a curvature radius of greater than or equal to 1 mm and less than or equal to 100 mm is obtained. The display device can be miniaturized by being foldable. In addition, in the state where the flexible display panel is opened, display which is unbroken and continuous over a plurality of housings is possible. The plurality of housings can store a circuit, an electronic component, a battery and the like inside as appropriate, and the thickness of each housing can be small.

Description

TECHNICAL FIELD

The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a lighting device, driving methods thereof, or manufacturing methods thereof. In particular, one embodiment of the present invention relates to an electronic device, an information processor, and a communication information device, each of which has a display device, or manufacturing methods thereof.

BACKGROUND ART

The social infrastructures relating to means for transmitting information have advanced. This has made it possible to acquire, process, and send out many pieces and various kinds of information with the use of an information processor not only at home or office but also at other visiting places.

Under the circumstance, portable information processors such as a smartphone, a tablet, and a phablet are under active development. For example, an electronic device using a flexible display panel has been known (Patent Document 1). In addition, a multi-panel electronic device has been known (Patent Document 2).

PATENT DOCUMENT

• [Patent Document 1] Japanese Published Patent Application No. 2012-190794
• [Patent Document 2] Japanese Published Patent Application No. 2012-502372

DISCLOSURE OF INVENTION

An object of one embodiment of the present invention is to provide a novel foldable display device or an electronic device using such a display device, e.g., a portable information processor or a portable communication information device. Another object of one embodiment of the present invention is to provide a miniaturized display device. Another object of one embodiment of the present invention is to provide a display device capable of unbroken, continuous display. Another object of one embodiment of the present invention is to provide a thinned display device. Another object of one embodiment of the present invention is to provide a novel display device.

Note that the descriptions of these objects do not disturb the existence of other objects. In one embodiment of the present invention, there is no need to achieve all the objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.

In one embodiment, a foldable display device of which a display panel can be folded n times (n≥1, and n is a natural number) at a curvature radius of greater than or equal to 1 mm and less than or equal to 100 mm is provided.

In one embodiment, a flexible display panel includes a first portion supported by a first housing, a second portion supported by a second housing, and a bend portion between the first portion and the second portion. A first circuit (or electronic component) is provided in the first housing supporting the first portion. A second circuit (or electronic component) is provided in the second housing supporting the second portion. When the flexible display panel is folded (or bent) at the bend portion, the first housing and the second housing overlap with each other. The first circuit (or electronic component) and the second circuit (or electronic component) may have different functions from each other. Alternatively, the first circuit (or electronic component) and the second circuit (or electronic component) may have the same functions.

In one embodiment, a flexible display panel includes first to third portions respectively supported by first to third housings, a first bend portion between the first portion and the second portion, and a second bend portion between the second portion and the third portion. When the flexible display panel is folded, the first to third portions overlap with one another. In that state, any one of the first to third portions appears on the top surface, and a driving mode is possible in which at least display of the portion appearing atop is selectively on and display of the other portions is off. A first circuit (or electronic component) is provided in one housing among the first to third housings respectively supporting the first to third portions, and a second circuit (or electronic component) is provided in another housing among the first to third housings respectively supporting the first to third portions. Furthermore, although a third circuit (or electronic component) may be provided in still another housing, any circuit (or electronic component) need not necessarily be provided in that housing. In the state where the flexible display panel is folded, not only display of the first portion on the top surface but also display of the bend portion connecting to the first portion can be selectively on.

In any of the above embodiments, the first circuit (or electronic component) and the second circuit (or electronic component) may be connected to each other through a wiring. This wiring may be directly provided in or on the flexible display panel. Alternatively, this wiring may be provided in a flexible substrate or sheet that is provided to overlap with the flexible display panel. Further alternatively, the first circuit (or electronic component) and the second circuit (or electronic component) may communicate signals wirelessly.

The display device can be miniaturized by being foldable. In addition, in the state where the flexible display panel is opened, display which is unbroken and continuous over a plurality of housings is possible. The plurality of housings can store a circuit, an electronic component, a battery and the like inside as appropriate, and the thickness of each housing can be small. Note that one embodiment of the present invention is not limited to these effects. For example, depending on circumstances or conditions, one embodiment of the present invention might produce another effect. Furthermore, depending on circumstances or conditions, one embodiment of the present invention might not produce any of the above effects.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C illustrate a display device:

FIG. 2 illustrates a display device:

FIGS. 3A and 3B illustrate a display device;

FIGS. 4A and 4B illustrate a display device;

FIGS. 5A and 5B illustrate a display device;

FIG. 6 illustrates a smartphone:

FIGS. 7A and 7B illustrate a display panel:

FIGS. 8A and 8B illustrate a display panel;

FIGS. 9A and 9B illustrate a display panel;

FIGS. 10A and 10B illustrate a display panel;

FIGS. 11A to 11C illustrate a method for manufacturing a display panel;

FIGS. 12A to 12C illustrate a method for manufacturing a display panel; and

FIGS. 13A to 13C illustrate an example of an electronic device.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments will be described in detail with reference to drawings. Note that the present invention is not limited to the description below, and it is easily understood by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not interpreted as being limited to the content of the embodiments below. Note that in the structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description of such portions is not repeated.

Embodiment 1

In this embodiment, a structure of a display device of one embodiment of the present invention will be described with reference toFIGS. 1A to 1C,FIG. 2, andFIGS. 3A and 3B. In this embodiment, a display device that can be folded in three, in other words, a display device having two bend portions, will be described. Note that one embodiment of the present invention need not be limited to a display device folded in three, and a display device folded in two, four, five, or more is possible. In addition, a way of folding a display panel is not limited to the embodiment. For example, a display panel can be folded such that not the leftmost portion but the rightmost portion becomes the top surface or the center portion becomes the top surface.

FIG. 1A to 1C are conceptual diagrams of a display device of this embodiment.FIG. 1A shows a state where a flexible display panel is opened.FIG. 1B shows a state where the flexible display panel that is being opened or being folded.FIG. 1C shows a state where the flexible display panel is folded. In each ofFIG. 1A to 1C, the display surface faces upside.FIG. 2 shows the display device in a state where the display panel is opened.FIGS. 3A and 3B show cross-sectional views taken along dashed-dotted line C-D inFIG. 1C, which are in a state where the flexible panel is folded (hereinafter such state may also be referred to as close state).

A component such as a switch (not shown) for detecting an open/close state of the display panel may be provided in at least one of housings.

InFIG. 3A, which is in a state where the display panel is folded, the following driving may be performed: a region of the top surface of the display panel and a region of the side surface of the display panel connecting to the top surface region (that is, a region on the right side of the top surface display region) is selectively used as a display region and the other portions are not used as a display region. In this way, unnecessary power consumption can be prevented in the state where the display panel is folded.

Housings (or frames)111-1,112-1, and113-1 supporting the display panel are provided on an underside (rear side) of aflexible display panel101. These housings can store a circuit, an electronic component, a battery and the like inside. The housings may be formed using a metal, a resin, a rubber, or a combination thereof to have a function of protecting the display panel, or a circuit or an electronic component stored inside, from the impact of hitting or drop.

Frame members111-2,112-2, and113-2 are provided on an upper side (display surface side) of a periphery of theflexible display panel101. The flexible display panel is sandwiched between the housings on the underside and the corresponding frame members on the upper side, thereby being supported. The material of the frame members may be the same as the material of the housings.

Each of the frame members and the corresponding housing may be fixed to each other by means of an adhesive, a screw, or the like. Alternatively, each of the frame members and the corresponding housing may be formed as one component using the same material. In that case, such a component may have a groove in which the display panel is set, thereby holding the display panel. In this embodiment,side frame members128 and129 are provided. The side frame members may be formed using a material such as a metal, a resin, or a rubber.

The curvature radius at the bend portion may be greater than or equal to 1 mm and less than or equal to 100 mm.

A circuit or electronic component (121 or122) such as a control unit, a power supply unit, a storage battery, or an antenna is stored in at least one of the housings111-1,112-1, and113-1. An FPC (flexible printed circuit substrate)125 may be used for the connection between the circuit or electronic component and the display panel.

The housings111-1,112-1, and113-1 may be directly fixed to the display panel with an adhesive or the like. Alternatively, a flexible substrate that protects the display panel or has a function of leading a wiring may be provided between the display panel and the housings.

In this embodiment, an example in which a flexible substrate102-1 is provided between the display panel and the housings is shown. The flexible substrate102-1 has approximately the same size as the display panel, and has also a function of connecting the housings. In order to connect the FPC extending from the display panel with the housing, part of the flexible substrate may be cut off or the size of the flexible substrate may be a little smaller than the display panel. The material of the flexible substrate102-1 may be a resin, a rubber or the like, in which case the mechanical strength of the bend portion can be supplemented. Furthermore, a wiring for connecting the circuits or electronic components provided in the housings is provided in the flexible substrate102-1.

A flexible substrate102-2 may be provided between the display panel and the frame members on the upper side. General FPC substrates may be used as the flexible substrates102-1 and102-2. Note that both of or either one of the flexible substrates102-1 and102-2 may be omitted.

TheFPC125 is provided on theflexible display panel101, and is connected to a driver circuit of the display panel or the like, which is provided in the housing. Although not limited to this, theFPC125 may be connected to the driver circuit provided in the housing through anopening133 of the housing.

FIG. 3B shows a modification example of this embodiment, in which a housing112-1 is thinner than housings111-1 and113-1. This embodiment can be combined with any of the other embodiments in this specification as appropriate.

Embodiment 2

In this embodiment, configurations of display devices each of which is one embodiment of the present invention will be described with reference toFIGS. 4A and 4B andFIGS. 5A and 5B. Note that some components similar to those of the display device described in Embodiment 1 can also be used in this embodiment. For such components, the description in Embodiment 1 is referred to.

In this embodiment, as an example, abattery unit121 is stored in a housing111-1, and a main substrate including a control unit for controlling a display panel and an electronic device as a whole is stored in a housing113-1. A housing112-1 may be a dummy housing that does not store any circuit or electronic component. Storing a plurality of components in a plurality of different housings, as in this embodiment, can make the thicknesses of the housings evenly thin. In this embodiment, the thicknesses of all the housings are the same, in which case a display surface can easily be flat when the display panel is opened.

Wirings (including a line leading power supply, in this embodiment) are provided in a flexible substrate102-1, and power is supplied from thebattery unit121 in the housing111-1 to thecontrol unit122 in the housing113-1. An example of the flexible substrate102-1 in which the wirings are provided is shown inFIGS. 4A and 4B. InFIG. 4A, areference numeral130 denotes a wiring and areference numeral131 denotes a terminal portion. Thewiring130 is connected to the battery or the control unit stored in the housing through anopening132 of the housing. Note that a display panel on the upper side of the flexible substrate102-1 and components thereover are not shown inFIG. 4A for explanation. Although an example in which one long opening extends is shown inFIG. 4A, the shape and the number of openings are not limited thereto. A plurality of openings may be provided as shown inFIG. 2.

FIGS. 5A and 5B show a modification example ofFIGS. 4A and 4B, in which the flexible substrate102-1 is omitted and awiring134 is directly provided in or on aflexible display panel101. For example, thewiring134 may be formed on the same substrate as the display panel with the use of a wiring layer constituting gate electrodes or source/drain electrodes of transistors included in the display panel and/or some other wiring layers formed on the same substrate as the transistors, and may be connected to a circuit in a housing by anFPC135. As another modification example, a battery unit can be stored in each of the housing112-1 and the housing111-1 inFIGS. 4A and 4B andFIGS. 5A and 5B. In such a case, the display device can be used for a longer period of time even without charging a storage battery.

This embodiment can be combined with any of the other embodiments in this specification as appropriate.

Embodiment 3

In this embodiment, an example of a portable communication device such as a smartphone (mobile phone with advanced features), a tablet with a telephone function, or a phablet will be described.FIG. 6 shows a general configuration of a smartphone. In general, the smartphone includes amain substrate600, aspeaker601, acamera602, adisplay panel603, abattery unit604, an antenna forportable communication605, an antenna forNFC606, and the like. On themain substrate600, various ICs and electronic components such as a passive element are mounted. For example, aquartz crystal unit611, aDRAM612, anapplication processor613, abaseband processor614, anelectronic compass615, aquartz crystal unit616, anRF transceiver IC617, a touchpanel control IC618, anacceleration sensor619, a wireless LAN/Bluetooth (registered trademark)module620, a powersupply control IC621, a power amplifier for W-CDMA622, aflash memory623, afilter624, and the like are mounted. For the sake of convenience, these components are hereinafter collectively called control unit. Note that not all of these circuits or electronic components need to be mounted on the main substrate, and some of components or circuits may be mounted on a different substrate as appropriate. The display panel is flexible and can be folded.

The main substrate and various electronic components are stored in a plurality of different housings as appropriate. In the display device of Embodiment 2, as an example, thebattery unit604 and the antenna forNFC606 are stored in the housing113-1, and themain substrate600 and the antenna forportable communication605 are stored in the housing111-1. In this way, the housing where thebattery unit604 is stored has room for increasing the capacity of a secondary battery. Although there is no need to limit the way thecamera602 is used, it can be used in the following way: the camera is mounted on the housing113-1 and when the display device is in a close state, a user takes a picture with the camera while seeing an object to be pictured, which is displayed on the display panel over the housing111-1, the display panel on the opposite side of the display device from the camera.

Embodiment 4

In this embodiment, a display panel using an active matrix electroluminescence (EL) display device will be described as an example of a flexible display panel of one embodiment of the present invention, with reference toFIGS. 7A and 7B,FIGS. 8A and 8B,FIGS. 9A and 9B,FIGS. 10A and 10B,FIGS. 1A to 11C, andFIGS. 12A to 12C. Note that the display panel is not limited to an EL display device, and other kinds of display devices such as a liquid crystal display device and an electrophoretic display device may also be used.

Specific Example 1

FIG. 7A shows a plan view of aflexible display panel101, andFIG. 7B shows an example of a cross-sectional view taken along dashed-dotted line A1-A2 inFIG. 7A.

The display panel shown inFIG. 7B includes anelement layer1101, abonding layer1105, and asubstrate1103. Theelement layer1101 includes asubstrate1201, abonding layer1203, an insulatinglayer1205, a plurality oftransistors1240, aconductive layer1157, an insulatinglayer1207, an insulatinglayer1209, a plurality of light-emittingelements1230, an insulatinglayer1211, asealing layer1213, an insulatinglayer1261, acoloring layer1259, a light-blocking layer1257, and an insulatinglayer1255.

Theconductive layer1157 is electrically connected to anFPC1108 via aconnector1215.

A light-emittingelement1230 includes alower electrode1231, anEL layer1233, and anupper electrode1235. The EL layer is formed of an organic light-emitting material. Thelower electrode1231 is electrically connected to a source electrode or a drain electrode of thetransistor1240. An end portion of thelower electrode1231 is covered with the insulatinglayer1211. The light-emittingelement1230 has a top emission structure. Theupper electrode1235 has a light-transmitting property and transmits light emitted from theEL layer1233.

Thecoloring layer1259 is provided to overlap with the light-emittingelement1230, and the light-blocking layer1257 is provided to overlap with the insulatinglayer1211. Thecoloring layer1259 and the light-blocking layer1257 are covered with the insulatinglayer1261. The space between the light-emittingelement1230 and the insulatinglayer1261 is filled with thesealing layer1213.

The display panel includes a plurality of transistors in alight extraction portion1104 and adriver circuit portion1106. Thetransistor1240 is provided over the insulatinglayer1205. The insulatinglayer1205 and thesubstrate1201 are attached to each other with thebonding layer1203. The insulatinglayer1255 and thesubstrate1103 are attached to each other with thebonding layer1105. It is preferable to use films with low water permeability for the insulatinglayer1205 and the insulatinglayer1255, in which case an impurity such as water can be prevented from entering the light-emittingelement1230 or thetransistor1240, leading to improved reliability of the display panel. Thebonding layer1203 can be formed using a material similar to that of thebonding layer1105.

The display panel in Specific Example 1 can be manufactured in the following manner: the insulatinglayer1205, thetransistor1240, and the light-emittingelement1230 are formed over a formation substrate with high heat resistance; the formation substrate is detached; and the insulatinglayer1205, thetransistor1240, and the light-emittingelement1230 are transferred to thesubstrate1201 and attached thereto with the use of thebonding layer1203. Furthermore, the display panel in Specific Example 1 can be manufactured in the following manner: the insulatinglayer1255, thecoloring layer1259, and the light-blocking layer1257 are formed over a formation substrate with high heat resistance; the formation substrate is detached; and the insulatinglayer1255, thecoloring layer1259, and the light-blocking layer1257 are transferred to thesubstrate1103 and attached thereto with the use of thebonding layer1105.

In the case where a material with high water permeability and low heat resistance (e.g., resin) is used for a substrate, it is impossible to expose the substrate to high temperature in the manufacturing process. Thus, there is a limitation on conditions for forming a transistor and an insulating film over the substrate. In the manufacturing method of this embodiment, a transistor and the like can be formed over a formation substrate with high heat resistance; thus, a highly reliable transistor and an insulating film with sufficiently low water permeability can be formed. Then, the transistor and the insulating film are transferred to thesubstrate1103 and thesubstrate1201, whereby a highly reliable display panel can be manufactured. Therefore, with one embodiment of the present invention, a thin or/and lightweight active matrix light-emitting device with high reliability can be provided. Details of the manufacturing method thereof will be described later.

Thesubstrate1103 and thesubstrate1201 are each preferably formed using a material with high toughness. In that case, a display device with high impact resistance that is less likely to be broken can be provided. For example, when thesubstrate1103 is an organic resin substrate and thesubstrate1201 is a substrate formed using a thin metal material or a thin alloy material, the display panel can be lightweight and less likely to be broken, as compared with the case where a glass substrate is used.

A metal material and an alloy material, which have high thermal conductivity, are preferred because they can easily conduct heat to the whole substrate and accordingly can prevent a local temperature rise in the display panel. The thickness of a substrate using a metal material or an alloy material is preferably greater than or equal to 10 μm and less than or equal to 200 μm, further preferably greater than or equal to 20 μm and less than or equal to 50 μm.

Furthermore, when a material with high thermal emissivity is used for thesubstrate1201, the surface temperature of the display panel can be prevented from rising, leading to prevention of breakage or a decrease in reliability of the display panel. For example, thesubstrate1201 may have a stacked structure of a metal substrate and a layer with high thermal emissivity (the layer can be formed using a metal oxide or a ceramic material, for example). In the following specific examples, description of components similar to those in Specific Example 1 is omitted.

Specific Example 2

FIG. 8A shows another example of alight extraction portion1104 in a display panel. The display panel shown inFIG. 8A is capable of touch operation.

The display panel shown inFIG. 8A includes anelement layer1101, abonding layer1105, and asubstrate1103. Theelement layer1101 includes asubstrate1201, abonding layer1203, an insulatinglayer1205, a plurality of transistors, an insulatinglayer1207, an insulatinglayer1209, a plurality of light-emitting elements, an insulatinglayer1211, an insulatinglayer1217, asealing layer1213, an insulatinglayer1261, acoloring layer1259, a light-blocking layer1257, a plurality of light-receiving elements, aconductive layer1281, aconductive layer1283, an insulatinglayer1291, an insulatinglayer1293, an insulatinglayer1295, and an insulatinglayer1255.

In Specific Example 2, the insulatinglayer1217 is provided over the insulatinglayer1211. With the provision of the insulatinglayer1217, the space between thesubstrate1103 and thesubstrate1201 can be adjusted.

FIG. 8A shows an example in which the light-receiving element is provided between the insulatinglayer1255 and thesealing layer1213. Since the light-receiving element can be placed to overlap with a non-light-emitting region (e.g., a region where atransistor1240 or a wiring is provided) on thesubstrate1201 side, the display panel can be provided with a touch sensor without a decrease in the aperture ratio of a pixel (light-emitting element).

As the light-receiving element included in the display panel, for example, a PN photodiode or a PIN photodiode can be used. In this embodiment, a PIN photodiode including a p-type semiconductor layer1271, an i-type semiconductor layer1273, and an n-type semiconductor layer1275 is used as the light-receiving element.

Note that the i-type semiconductor layer1273 is a semiconductor in which the concentration of each of an impurity imparting p-type conductivity and an impurity imparting n-type conductivity is 1×10²⁰cm⁻³or less and which has photoconductivity 100 times or more as high as dark conductivity. The i-type semiconductor layer1273 also includes, in its category, a semiconductor that contains an impurity element belonging to Group 13 or Group 15 of the periodic table. In other words, since an i-type semiconductor has weak n-type electric conductivity when an impurity element for controlling valence electrons is not added intentionally, the i-type semiconductor layer1273 includes, in its category, a semiconductor to which an impurity element imparting p-type conductivity is added intentionally or unintentionally at the time of deposition or after the deposition.

The light-blocking layer1257 is overlapped with the light-receiving element on thesubstrate1103 side. The light-blocking layer1257 between the light-receiving element and thesealing layer1213 can prevent the light-receiving element from being irradiated with light emitted from the light-emittingelement1230.

Each of theconductive layer1281 and theconductive layer1283 is electrically connected to the light-receiving element. For theconductive layer1281, a conductive layer that transmits light incident on the light-receiving element is preferably used. For theconductive layer1283, a conductive layer that blocks light incident on the light-receiving element is preferably used.

It is preferable to provide an optical touch sensor between thesubstrate1103 and thesealing layer1213 because the optical touch sensor is less likely to be affected by light emitted from the light-emittingelement1230 and can have improved S/N ratio.

Specific Example 3

FIG. 8B shows another example of alight extraction portion1104 in a display panel. The display panel shown inFIG. 8B is capable of touch operation.

The display panel shown inFIG. 8B includes anelement layer1101, abonding layer1105, and asubstrate1103. Theelement layer1101 includes asubstrate1201, abonding layer1203, an insulatinglayer1205, a plurality of transistors, an insulatinglayer1207, an insulatinglayer1209a, an insulatinglayer1209b, a plurality of light-emitting elements, an insulatinglayer1211, an insulatinglayer1217, asealing layer1213, acoloring layer1259, a light-blocking layer1257, a plurality of light-receiving elements, aconductive layer1280, aconductive layer1281, and an insulatinglayer1255.

FIG. 8B shows an example in which a light-receiving element is provided between the insulatinglayer1205 and thesealing layer1213. Since the light-receiving element is provided between the insulatinglayer1205 and thesealing layer1213, a conductive layer to which the light-receiving element is electrically connected and a photoelectric conversion layer included in the light-receiving element can be formed using the same materials through the same steps as a conductive layer and a semiconductor layer included in atransistor1240. Thus, the display panel capable of touch operation can be manufactured without a significant increase in the number of manufacturing steps.

Specific Example 4

FIG. 9A shows another example of a display panel. The display panel shown inFIG. 9A is capable of touch operation.

The display panel shown inFIG. 9A includes anelement layer1101, abonding layer1105, and asubstrate1103. Theelement layer1101 includes asubstrate1201, abonding layer1203, an insulatinglayer1205, a plurality of transistors, aconductive layer1156, aconductive layer1157, an insulatinglayer1207, an insulatinglayer1209, a plurality of light-emitting elements, an insulatinglayer1211, an insulatinglayer1217, asealing layer1213, acoloring layer1259, a light-blocking layer1257, an insulatinglayer1255, aconductive layer1272, aconductive layer1274, an insulatinglayer1276, an insulatinglayer1278, aconductive layer1294, and aconductive layer1296.

FIG. 9A shows an example in which a capacitive touch sensor is provided between the insulatinglayer1255 and thesealing layer1213. The capacitive touch sensor includes theconductive layer1272 and theconductive layer1274.

Theconductive layer1156 and theconductive layer1157 are electrically connected to anFPC1108 via aconnector1215. Theconductive layer1294 and theconductive layer1296 are electrically connected to theconductive layer1274 viaconductive particles1292. Thus, the capacitive touch sensor can be driven via theFPC1108.

Specific Example 5

FIG. 9B shows another example of a display panel. The display panel shown inFIG. 9B is capable of touch operation.

The display panel shown inFIG. 9B includes anelement layer1101, abonding layer1105, and asubstrate1103. Theelement layer1101 includes asubstrate1201, abonding layer1203, an insulatinglayer1205, a plurality of transistors, aconductive layer1156, aconductive layer1157, an insulatinglayer1207, an insulatinglayer1209, a plurality of light-emitting elements, an insulatinglayer1211, an insulatinglayer1217, asealing layer1213, acoloring layer1259, a light-blocking layer1257, an insulatinglayer1255, aconductive layer1270, aconductive layer1272, aconductive layer1274, an insulatinglayer1276, and an insulatinglayer1278.

FIG. 9B shows an example in which a capacitive touch sensor is provided between the insulatinglayer1255 and thesealing layer1213. The capacitive touch sensor includes theconductive layer1272 and theconductive layer1274.

Theconductive layer1156 and theconductive layer1157 are electrically connected to anFPC1108avia aconnector1215a. Theconductive layer1270 is electrically connected to anFPC1108bvia aconnector1215b. Thus, a light-emittingelement1230 and atransistor1240 can be driven via theFPC1108a, and the capacitive touch sensor can be driven via theFPC1108b.

Specific Example 6

FIG. 10A shows another example of alight extraction portion1104 in a display panel.

Thelight extraction portion1104 inFIG. 10A includes asubstrate1103, abonding layer1105, asubstrate1202, an insulatinglayer1205, a plurality of transistors, an insulatinglayer1207, aconductive layer1208, an insulatinglayer1209a, an insulatinglayer1209b, a plurality of light-emitting elements, an insulatinglayer1211, asealing layer1213, and acoloring layer1259.

A light-emittingelement1230 includes alower electrode1231, anEL layer1233, and anupper electrode1235. Thelower electrode1231 is electrically connected to a source electrode or a drain electrode of atransistor1240 via theconductive layer1208. An end portion of thelower electrode1231 is covered with the insulatinglayer1211. The light-emittingelement1230 has a bottom emission structure. Thelower electrode1231 has a light-transmitting property and transmits light emitted from theEL layer1233.

Acoloring layer1259 is provided in a place overlapped with the light-emittingelement1230, and light emitted from the light-emittingelement1230 is extracted from thesubstrate1103 side through thecoloring layer1259. The space between the light-emittingelement1230 and thesubstrate1202 is filled with thesealing layer1213. Thesubstrate1202 can be formed using a material similar to that of thesubstrate1201.

Specific Example 7

FIG. 10B shows another example of a display panel.

The display panel shown inFIG. 10B includes anelement layer1101, abonding layer1105, and asubstrate1103. Theelement layer1101 includes asubstrate1202, an insulatinglayer1205, aconductive layer1310a, aconductive layer1310b, a plurality of light-emitting elements, an insulatinglayer1211, aconductive layer1212, and asealing layer1213.

Theconductive layer1310aand theconductive layer1310b, which are external connection electrodes of the display panel, can each be electrically connected to an FPC or the like.

A light-emittingelement1230 includes alower electrode1231, anEL layer1233, and anupper electrode1235. An end portion of thelower electrode1231 is covered with the insulatinglayer1211. The light-emittingelement1230 has a bottom emission structure. Thelower electrode1231 has a light-transmitting property and transmits light emitted from theEL layer1233. Theconductive layer1212 is electrically connected to thelower electrode1231.

Thesubstrate1103 may have, as a light extraction structure, a hemispherical lens, a micro lens array, a film provided with an uneven surface structure, a light diffusing film, or the like. For example, thesubstrate1103 with a light extraction structure can be formed by attaching the above lens or film to a resin substrate with an adhesive or the like having substantially the same refractive index as the substrate or the lens or film.

Theconductive layer1212 is preferably, though not necessarily, provided because voltage drop due to the resistance of thelower electrode1231 can be prevented. In addition, for a similar purpose, a conductive layer electrically connected to theupper electrode1235 may be provided over the insulatinglayer1211.

Theconductive layer1212 can be a single layer or a stacked layer formed using a material selected from copper, titanium, tantalum, tungsten, molybdenum, chromium, neodymium, scandium, nickel, or aluminum, or an alloy material containing any of these materials as its main component. The thickness of theconductive layer1212 can be greater than or equal to 0.1 μm and less than or equal to 3 μm, preferably greater than or equal to 0.1 μm and less than or equal to 0.5 μm.

When a paste (e.g., silver paste) is used as a material for the conductive layer electrically connected to theupper electrode1235, metal particles forming the conductive layer aggregate; therefore, the surface of the conductive layer is rough and has many gaps. Thus, it is difficult for theEL layer1233 to completely cover the surface of the conductive layer; accordingly, the upper electrode and an auxiliary wiring are electrically connected to each other easily, which is preferable.

<Examples of Materials>

Next, materials and the like that can be used for a display panel of one embodiment of the present invention will be described. Note that description on the components already described in this embodiment will be omitted.

Theelement layer1101 includes at least a light-emitting element. As the light-emitting element, a self-luminous element can be used, and an element whose luminance is controlled by current or voltage is included in the category of the light-emitting element. For example, a light-emitting diode (LED), an organic EL element, an inorganic EL element, or the like can be used.

Theelement layer1101 may further include a transistor for driving the light-emitting element, a touch sensor, or the like.

The structure of the transistors in the display panel is not particularly limited. For example, a forward staggered transistor or an inverted staggered transistor may be used. A top-gate transistor or a bottom-gate transistor may be used. A semiconductor material used for the transistors is not particularly limited, and for example, silicon or germanium can be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In—Ga—Zn-based metal oxide, may be used.

There is no particular limitation on the crystallinity of a semiconductor material used for the transistors, and an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single-crystal semiconductor, or a semiconductor partly including crystal regions) may be used. It is preferable that a semiconductor having crystallinity be used, in which case deterioration of the transistor characteristics can be suppressed.

The light-emitting element included in the display panel includes a pair of electrodes (thelower electrode1231 and the upper electrode1235); and theEL layer1233 between the pair of electrodes. One of the pair of electrodes functions as an anode and the other functions as a cathode.

The light-emitting element may have any of a top emission structure, a bottom emission structure, and a dual emission structure. A conductive film that transmits visible light is used as the electrode through which light is extracted. A conductive film that reflects visible light is preferably used as the electrode through which light is not extracted.

The conductive film that transmits visible light can be formed using, for example, indium oxide, indium tin oxide (ITO), indium zinc oxide, zinc oxide, or zinc oxide to which gallium is added. Alternatively, a film of a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, or titanium; an alloy containing any of these metal materials; or a nitride of any of these metal materials (e.g., titanium nitride) can be formed thin so as to have a light-transmitting property. Alternatively, a stack of any of the above materials can be used as the conductive layer. For example, a stacked film of ITO and an alloy of silver and magnesium is preferably used, in which case conductivity can be increased. Further alternatively, graphene or the like may be used.

For the conductive film that reflects visible light, for example, a metal material, such as aluminum, gold, platinum, silver, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or an alloy including any of these metal materials can be used. Lanthanum, neodymium, germanium, or the like may be added to the metal material or the alloy. Furthermore, an alloy containing aluminum (an aluminum alloy) such as an alloy of aluminum and titanium, an alloy of aluminum and nickel, or an alloy of aluminum and neodymium: or an alloy containing silver such as an alloy of silver and copper, an alloy of silver, copper, and palladium, or an alloy of silver and magnesium can be used for the conductive film. An alloy of silver and copper is preferable because of its high heat resistance. Moreover, a metal film or a metal oxide film is stacked on an aluminum alloy film, whereby oxidation of the aluminum alloy film can be suppressed. Examples of a material for the metal film or the metal oxide film are titanium and titanium oxide. Alternatively, the conductive film having a property of transmitting visible light and a film containing any of the above metal materials may be stacked. For example, a stacked film of silver and ITO or a stacked film of an alloy of silver and magnesium and ITO can be used.

Each of the electrodes may be formed by an evaporation method or a sputtering method. Alternatively, a discharging method such as an ink-jet method, a printing method such as a screen printing method, or a plating method may be used.

When a voltage higher than the threshold voltage of the light-emitting element is applied between thelower electrode1231 and theupper electrode1235, holes are injected to theEL layer1233 from the anode side and electrons are injected to theEL layer1233 from the cathode side. The injected electrons and holes are recombined in theEL layer1233 and a light-emitting substance contained in theEL layer1233 emits light.

TheEL layer1233 includes at least a light-emitting layer. In addition to the light-emitting layer, theEL layer1233 may further include one or more layers containing any of a material with a high hole-injection property, a material with a high hole-transport property, a hole-blocking material, a material with a high electron-transport property, a material with a high electron-injection property, a material with a bipolar property (a material with a high electron- and hole-transport property), and the like.

For theEL layer1233, either a low molecular compound or a high molecular compound can be used, and an inorganic compound may also be contained. Each of the above-described layers included in theEL layer1233 can be formed by any of the following methods: an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, a coating method, and the like.

In theelement layer1101, the light-emitting element is preferably provided between a pair of insulating films with low water permeability. Thus, an impurity such as water can be prevented from entering the light-emitting element, preventing a decrease in the reliability of the light-emitting device.

As an insulating film with low water permeability, a film containing nitrogen and silicon (e.g., a silicon nitride film or a silicon nitride oxide film), a film containing nitrogen and aluminum (e.g., an aluminum nitride film), or the like can be used. Alternatively, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film or the like can be used.

For example, the water vapor transmittance of the insulating film with low water permeability is lower than or equal to 1×10⁻⁵[g/m²·day], preferably lower than or equal to 1×10⁻⁶[μm²·day], further preferably lower than or equal to 1×10⁻⁷[g/m²·day], still further preferably lower than or equal to 1×10⁻⁸[g/m²·day].

Thesubstrate1103 has a light-transmitting property and transmits at least light emitted from the light-emitting element included in theelement layer1101. Thesubstrate1103 may be a flexible substrate. Moreover, the refractive index of thesubstrate1103 is higher than that of the air.

An organic resin, which is lighter than glass, is preferably used for thesubstrate1103, in which case the light-emitting device can be lightweight as compared with the case where glass is used.

Examples of a material having flexibility and a light-transmitting property with respect to visible light include a glass material that is thin enough to have flexibility, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, a polyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, a polyamide resin, a cycloolefin resin, a polystyrene resin, a polyamide imide resin, and a polyvinyl chloride resin. In particular, a material whose thermal expansion coefficient is low is preferred, and for example, a polyamide imide resin, a polyimide resin, or PET can be suitably used. A substrate in which a glass fiber is impregnated with an organic resin or a substrate whose thermal expansion coefficient is reduced by mixing an organic resin with an inorganic filler can also be used.

Thesubstrate1103 may have a stacked structure in which a hard coat layer (such as a silicon nitride layer) by which a surface of a light-emitting device is protected from damage, a layer (such as an aramid resin layer) which can disperse pressure, or the like is stacked over a layer of any of the above-mentioned materials. Furthermore, to suppress a decrease in the lifetime of the light-emitting element due to moisture and the like, the insulating film with low water permeability may be included in the stacked structure.

Thebonding layer1105 has a light-transmitting property and transmits at least light emitted from the light-emitting element included in theelement layer1101. The refractive index of thebonding layer1105 is higher than that of the air.

For thebonding layer1105, a resin that is curable at room temperature such as a two-component type resin, a light-curable resin, a heat-curable resin, or the like can be used. The examples include an epoxy resin, an acrylic resin, a silicone resin, a phenol resin, and the like. In particular, a material with low moisture permeability, such as an epoxy resin, is preferred.

Further, the resin may include a drying agent. For example, a substance which absorbs moisture by chemical adsorption, such as an oxide of an alkaline-earth metal (e.g., calcium oxide or barium oxide), can be used. Alternatively, a substance that adsorbs moisture by physical adsorption, such as zeolite or silica gel, may be used. The drying agent is preferably included because it can prevent an impurity such as moisture from entering the light-emitting element, thereby improving the reliability of the light-emitting device.

In addition, it is preferable to mix a filler with a high refractive index (e.g., titanium oxide) into the resin, in which case the efficiency of light extraction from the light-emitting element can be improved.

Thebonding layer1105 may also include a scattering member for scattering light. For example, thebonding layer1105 can be a mixture of the above resin and particles having a refractive index different from that of the resin. The particles function as the scattering member for scattering light.

The difference in refractive index between the resin and the particles with a refractive index different from that of the resin is preferably 0.1 or more, further preferably 0.3 or more. Specifically, an epoxy resin, an acrylic resin, an imide resin, silicone, or the like can be used as the resin, and titanium oxide, barium oxide, zeolite, or the like can be used as the particles.

Particles of titanium oxide or barium oxide are preferable because they scatter light excellently. When zeolite is used, it can adsorb water contained in the resin and the like, thereby improving the reliability of the light-emitting element.

The insulatinglayer1205 and the insulatinglayer1255 can each be formed using an inorganic insulating material. It is particularly preferable to use the insulating film with low water permeability, in which case a highly reliable display panel can be provided.

The insulatinglayer1207 has an effect of preventing diffusion of impurities into a semiconductor included in the transistor. As the insulatinglayers1207, an inorganic insulating film such as a silicon oxide film, a silicon oxynitride film, or an aluminum oxide film can be used.

As each of the insulatinglayers1209,1209a, and1209b, an insulating film with a planarization function is preferably selected in order to reduce surface unevenness due to the transistor or the like. For example, an organic material such as a polyimide resin, an acrylic resin, or a benzocyclobutene-based resin can be used. As an alternative to such an organic material, a low-dielectric constant material (a low-k material) or the like can be used. Note that a plurality of insulating films formed of these materials or inorganic insulating films may be stacked.

The insulatinglayer1211 is provided to cover an end portion of thelower electrode1231. In order that the insulatinglayer1211 be favorably covered with theEL layer1233 and theupper electrode1235 formed thereover, a side wall of the insulatinglayer1211 preferably has a tilted surface with continuous curvature.

As a material for the insulatinglayer1211, a resin or an inorganic insulating material can be used. As the resin, for example, a polyimide resin, a polyamide resin, an acrylic resin, a siloxane resin, an epoxy resin, or a phenol resin can be used. In particular, either a negative photosensitive resin or a positive photosensitive resin is preferably used for easy formation of the insulatinglayer1211.

There is no particular limitation on the method for forming the insulating layer1211: a photolithography method, a sputtering method, an evaporation method, a droplet discharging method (e.g., an inkjet method), a printing method (e.g., a screen printing method or an off-set printing method), or the like may be used.

The insulatinglayer1217 can be formed using an inorganic insulating material, an organic insulating material, a metal material, or the like. As the organic insulating material, for example, a negative or positive photosensitive resin, a non-photosensitive resin, or the like can be used. As the metal material, titanium, aluminum, or the like can be used. When a conductive material is used for the insulatinglayer1217 and the insulatinglayer1217 is electrically connected to theupper electrode1235, voltage drop due to the resistance of theupper electrode1235 can be prevented. The insulatinglayer1217 may have either a tapered shape or an inverse tapered shape.

Each of the insulatinglayers1276,1278,1291,1293, and1295 can be formed using an inorganic insulating material or an organic insulating material. It is particularly preferable to use an insulating film with a planarization function for each of the insulatinglayers1278 and1295 in order to reduce surface unevenness due to a sensor element.

For thesealing layer1213, a resin that is curable at room temperature such as a two-component type resin, a light-curable resin, a heat-curable resin, or the like can be used. For example, a polyvinyl chloride (PVC) resin, an acrylic resin, a polyimide resin, an epoxy resin, a silicone resin, a polyvinyl butyral (PVB) resin, an ethylene vinyl acetate (EVA) resin, or the like can be used. A drying agent may be contained in thesealing layer1213. In the case where light emitted from the light-emittingelement1230 is extracted outside through thesealing layer1213, thesealing layer1213 preferably includes a filler with a high refractive index or a scattering member. Materials for the drying agent, the filler with a high refractive index, and the scattering member are similar to those that can be used for thebonding layer1105.

Each of theconductive layers1156,1157,1294, and1296 can be formed using the same material and the same step as a conductive layer included in the transistor or the light-emitting element. Theconductive layer1280 can be formed using the same material and the same step as a conductive layer included in the transistor.

For example, each of the conductive layers can be formed to have a single-layer structure or a stacked-layer structure using any of metal materials such as molybdenum, titanium, chromium, tantalum, tungsten, aluminum, copper, neodymium, and scandium, and an alloy material containing any of these elements. Each of the conductive layers may be formed using a conductive metal oxide. As the conductive metal oxide, indium oxide (e.g., In₂O₃), tin oxide (e.g., SnO₂), zinc oxide (ZnO). ITO, indium zinc oxide (e.g., In₂O₃—ZnO), or any of these metal oxide materials in which silicon oxide is contained can be used.

Each of theconductive layers1208,1212,1310a, and1310bcan also be formed using any of the above metal materials, alloy materials, and conductive metal oxides.

Each of theconductive layers1272,1274,1281, and1283 is a conductive layer with a light-transmitting property. Each of them can be formed using, for example, indium oxide, ITO, indium zinc oxide, zinc oxide, zinc oxide to which gallium is added, or the like. Theconductive layer1270 can be formed using the same material and the same step as theconductive layer1272.

As theconductive particles1292, particles of an organic resin, silica, or the like coated with a metal material are used. It is preferable to use nickel or gold as the metal material because contact resistance can be decreased. It is also preferable to use particles each coated with layers of two or more kinds of metal materials, such as particles coated with nickel and further with gold.

For theconnector1215, it is possible to use a paste-like or sheet-like material in which a thermosetting resin is mixed with metal particles and which exhibits anisotropic electric conductivity is provided by thermocompression bonding. As the metal particles, particles in which two or more kinds of metals are layered, for example, nickel particles coated with gold are preferably used.

Thecoloring layer1259 is a colored layer that transmits light in a specific wavelength range. For example, a red (R) color filter for transmitting light in a red wavelength range, a green (G) color filter for transmitting light in a green wavelength range, a blue (B) color filter for transmitting light in a blue wavelength range, or the like can be used. Each coloring layer is formed in a desired position with any of various materials by a printing method, an inkjet method, an etching method using a photolithography method, or the like.

The light-blocking layer1257 is provided between the adjacent coloring layers1259. The light-blocking layer1257 blocks light emitted from the adjacent light-emitting element, thereby preventing color mixture between adjacent pixels. Here, thecoloring layer1259 is provided such that its end portion overlaps with the light-blocking layer1257, whereby light leakage can be reduced. The light-blocking layer1257 can be formed using a material that blocks light emitted from the light-emitting element, for example, a metal material, a resin material including a pigment or a dye, or the like. Note that the light-blocking layer1257 is preferably provided in a region other than thelight extraction portion1104, such as thedriver circuit portion1106, as illustrated inFIG. 7A, in which case undesired leakage of guided light or the like can be prevented.

The insulatinglayer1261 covering thecoloring layer1259 and the light-blocking layer1257 is preferably provided because it can prevent an impurity such as a pigment included in thecoloring layer1259 or the light-blocking layer1257 from diffusing into the light-emitting element or the like. For the insulatinglayer1261, a light-transmitting material is used, and an inorganic insulating material or an organic insulating material can be used. The insulating film with low water permeability may be used for the insulatinglayer1261.

<Manufacturing Method Example>

Next, an example of a method for manufacturing a display panel will be described with reference toFIGS. 11A to 11C andFIGS. 12A to 12C. Here, the manufacturing method is described using the display panel of Specific Example 1 (FIG. 7B) as an example.

First, aseparation layer1303 is formed over aformation substrate1301, and the insulatinglayer1205 is formed over theseparation layer1303. Then, the plurality of transistors, theconductive layer1157, the insulatinglayer1207, the insulatinglayer1209, the plurality of light-emitting elements, and the insulatinglayer1211 are formed over the insulatinglayer1205. An opening is formed in the insulatinglayers1211,1209, and1207 to expose the conductive layer1157 (FIG. 11A).

Aseparation layer1307 is formed over aformation substrate1305, and the insulatinglayer1255 is formed over theseparation layer1307. Then, the light-blocking layer1257, thecoloring layer1259, and the insulatinglayer1261 are formed over the insulating layer1255 (FIG. 11B).

Theformation substrate1301 and theformation substrate1305 can each be a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, a metal substrate, or the like.

For the glass substrate, for example, a glass material such as aluminosilicate glass, aluminoborosilicate glass, or barium borosilicate glass can be used. In the case where the temperature of heat treatment to be performed later is high, a substrate having a strain point of 730° C. or higher may be used.

In the case where a glass substrate is used as the formation substrate, an insulating film such as a silicon oxide film, a silicon oxynitride film, a silicon nitride film, or a silicon nitride oxide film is preferably formed between the formation substrate and the separation layer, in which case contamination from the glass substrate can be prevented.

Theseparation layer1303 and theseparation layer1307 each have a single-layer structure or a stacked-layer structure containing an element selected from tungsten, molybdenum, titanium, tantalum, niobium, nickel, cobalt, zirconium, zinc, ruthenium, rhodium, palladium, osmium, iridium, and silicon; an alloy material containing any of the elements; or a compound material containing any of the elements. A crystal structure of a layer containing silicon may be any of amorphous, microcrystal, and polycrystal.

The separation layer can be formed by a sputtering method, a plasma CVD method, a coating method, a printing method, or the like. Note that a coating method includes a spin coating method, a droplet discharge method, and a dispensing method.

In the case where the separation layer has a single-layer structure, a tungsten layer, a molybdenum layer, or a layer containing a mixture of tungsten and molybdenum is preferably formed. Alternatively, a layer containing an oxide or an oxynitride of tungsten, a layer containing an oxide or an oxynitride of molybdenum, or a layer containing an oxide or an oxynitride of a mixture of tungsten and molybdenum may be formed. Note that a mixture of tungsten and molybdenum is an alloy of tungsten and molybdenum, for example.

In the case where the separation layer is formed to have a stacked-layer structure including a layer containing tungsten and a layer containing an oxide of tungsten, the layer containing an oxide of tungsten may be formed as follows: the layer containing tungsten is formed first and an insulating film formed of an oxide is formed thereover, so that the layer containing an oxide of tungsten is formed at the interface between the tungsten layer and the insulating film. Alternatively, the layer containing an oxide of tungsten may be formed by performing thermal oxidation treatment, oxygen plasma treatment, nitrous oxide (N₂O) plasma treatment, treatment with a highly oxidizing solution such as ozone water, or the like on the surface of the layer containing tungsten. Plasma treatment or heat treatment may be performed in an atmosphere of oxygen, nitrogen, or nitrous oxide alone, or a mixed gas of any of these gasses and another gas. Surface condition of the separation layer is changed by the plasma treatment or heat treatment, whereby adhesion between the separation layer and the insulating film formed later can be controlled.

Each of the insulating layers can be formed by a sputtering method, a plasma CVD method, a coating method, a printing method, or the like. For example, the insulating layer is formed at a temperature of higher than or equal to 250° C. and lower than or equal to 400° C. by a plasma CVD method, whereby the insulating layer can be a dense film with very low water permeability.

Then, a material for thesealing layer1213 is applied to a surface of theformation substrate1305 over which thecoloring layer1259 and the like are formed or a surface of theformation substrate1301 over which the light-emittingelement1230 and the like are formed, and theformation substrate1301 and theformation substrate1305 are attached so that these two surfaces face each other with thesealing layer1213 positioned therebetween (FIG. 11C).

Next, theformation substrate1301 is separated, and the exposed insulatinglayer1205 and thesubstrate1201 are attached to each other with the use of thebonding layer1203. Furthermore, theformation substrate1305 is separated, and the exposed insulatinglayer1255 and thesubstrate1103 are attached to each other with the use of thebonding layer1105. Although thesubstrate1103 does not overlap with theconductive layer1157 inFIG. 12A, thesubstrate1103 may overlap with theconductive layer1157.

Any of a variety of methods can be used as appropriate for the separation process. For example, when a layer including a metal oxide film is formed as the separation layer so as to be in contact with the layer to be separated, the metal oxide film is embrittled by crystallization, whereby the layer to be separated can be separated from the formation substrate. Alternatively, when an amorphous silicon film containing hydrogen is formed as the separation layer between a formation substrate having high heat resistance and a layer to be separated, the amorphous silicon film is removed by laser light irradiation or etching, whereby the layer to be separated can be separated from the formation substrate. Alternatively, after a layer including a metal oxide film in contact with the layer to be separated is formed, the metal oxide film is embrittled by crystallization, and part of the separation layer is removed by etching using a solution or a fluoride gas such as NF₃, BrF₃, or ClF₃, whereby the separation can be performed at the embrittled metal oxide film. Alternatively, a method carried out as follows may be employed: a film containing nitrogen, oxygen, hydrogen, or the like (e.g., an amorphous silicon film containing hydrogen, an alloy film containing hydrogen, an alloy film containing oxygen, or the like) is used as the separation layer, and the separation layer is irradiated with laser light to release the nitrogen, oxygen, or hydrogen contained in the separation layer as gas, thereby promoting separation between the layer to be separated and the formation substrate. Alternatively, it is possible to use a method in which the formation substrate provided with the layer to be separated is removed mechanically or by etching using a solution or a fluoride gas such as NF₃, BrF₃, or ClF₃, or the like. In this case, the separation layer is not necessarily provided.

When a plurality of the above-described separation methods is combined, the separation process can be conducted easily. In other words, separation can be performed with physical force (by a machine or the like) after performing laser light irradiation, etching on the separation layer with a gas, a solution, or the like, or mechanical removal with a sharp knife, scalpel or the like so that the separation layer and the layer to be separated can be easily separated from each other.

Separation of the layer to be separated from the formation substrate may be carried out by soaking the interface between the separation layer and the layer to be separated in a liquid. Furthermore, the separation may be conducted while a liquid such as water is being poured.

As another separation method, in the case where the separation layer is formed using tungsten, it is preferable that the separation be performed while etching the separation layer using a mixed solution of ammonium water and a hydrogen peroxide solution.

Note that the separation layer is not necessarily provided in the case where separation at an interface between the formation substrate and the layer to be separated is possible. For example, glass is used as the formation substrate, an organic resin such as polyimide is formed in contact with the glass, and an insulating film, a transistor, and the like are formed over the organic resin. In this case, heating the organic resin enables the separation at the interface between the formation substrate and the organic resin. Alternatively, separation at the interface between a metal layer and the organic resin may be performed in the following manner: the metal layer is provided between the formation substrate and the organic resin and current is made to flow in the metal layer so that the metal layer is heated.

Lastly, an opening is formed in the insulatinglayer1255 and thesealing layer1213 to expose the conductive layer1157 (FIG. 12B). In the case where thesubstrate1103 overlaps with theconductive layer1157, the opening is formed also in thesubstrate1103 and the bonding layer1105 (FIG. 12C). The method for forming the opening is not particularly limited and may be, for example, a laser ablation method, an etching method, an ion beam sputtering method, or the like. As another method, a cut may be made in a film over theconductive layer1157 with a sharp knife or the like and part of the film may be separated by physical force.

In the above-described manner, the display panel of one embodiment of the present invention can be manufactured.

As described above, the display panel of this embodiment includes two substrates; one is thesubstrate1103 and the other is thesubstrate1201 or thesubstrate1202. The display panel can be formed with two substrates even when including a touch sensor. Owing to the use of the minimum number of substrates, improvement in light extraction efficiency and improvement in clarity of display can be easily achieved.

This embodiment can be combined with any of the other embodiments as appropriate.

Embodiment 5

In this embodiment, examples of an electronic device using the display device of one embodiment of the present invention will be described with reference to drawings.

As examples of electronic devices using a flexible display device, the following can be given: television devices (also called televisions or television receivers), monitors of computers or the like, digital cameras, digital video cameras, digital photo frames, mobile phones (also called cellular phones or mobile phone devices), portable game machines, portable information terminals, audio reproducing devices, large game machines, and the like.

FIGS. 13A and 13B illustrate atablet terminal9600 which can be folded in two. Note that, although an example in which the tablet terminal can be folded in two is shown here, a tablet terminal that can be folded in three, four, or more can also be fabricated. InFIG. 13A, thetablet terminal9600 is opened, and includes ahousing9630, adisplay portion9631, aswitch9626 for switching display modes, apower switch9627, aswitch9625 for switching to power-saving mode, afastener9629, and anoperation switch9628.

Thehousing9630 includes ahousing9630aand ahousing9630b, which are connected to each other with ahinge portion9639. Thehousing9630 can be folded in two by thehinge portion9639.

Adisplay portion9631 is formed over thehousing9630a, thehousing9630b, and thehinge portion9639. With the use of the flexible display panel disclosed in this specification and the like for thedisplay portion9631, a highly reliable tablet terminal with thedisplay portion9631 that is foldable can be obtained.

Part of thedisplay portion9631 can be atouchscreen region9632 and data can be input when a displayed operationkey panel9638 is touched. Thedisplay portion9631 may have a structure in which a half of the area has only a display function and the other half of the area has a touch panel function. Alternatively, all the area of thedisplay portion9631 may have a touch panel function. For example, keyboard buttons may be displayed on all the area of thedisplay portion9631 so that the tablet terminal is used as a data input terminal.

Theswitch9626 for switching a display mode allows switching between a landscape mode and a portrait mode, switching between color display and black-and-white display, and the like. Theswitch9625 for switching to power-saving mode can control display luminance to be optimal in accordance with the amount of external light in use of the tablet terminal which is detected by an optical sensor incorporated in the tablet terminal. In addition to the optical sensor, other sensing devices such as sensors for determining inclination, such as a gyroscope or an acceleration sensor, may be incorporated in the tablet terminal.

InFIG. 13B, thetablet terminal9600 is folded, and includes thehousing9630, asolar battery9633, and a charge anddischarge control circuit9634. Note thatFIG. 13B shows an example in which the charge anddischarge control circuit9634 includes abattery9635 and aDCDC converter9636.

With the use of the display device disclosed in this specification and the like for thedisplay portion9631, thedisplay portion9631 becomes foldable. For example, since thetablet terminal9600 can be folded in two, thehousing9630 can be closed when the tablet terminal is not used. Therefore, the tablet terminal is excellent in portability, and excellent in durability since thedisplay portion9631 can be protected when thehousing9630 is closed; accordingly, the tablet terminal is excellent in reliability in the light of long-term use.

The tablet terminal illustrated inFIGS. 13A and 13B can have other functions such as a function of displaying a variety of kinds of data (e.g., a still image, a moving image, and a text image), a function of displaying a calendar, a date, the time, or the like on the display portion, a touch-input function of operating or editing the data displayed on the display portion by touch input, and a function of controlling processing by a variety of kinds of software (programs).

Thesolar battery9633, which is attached on the surface of the tablet terminal, can supply electric power to the touch panel, the display portion, an image signal processor, and the like. Note that thesolar battery9633 can be provided on one or both surfaces of thehousing9630, so that thebattery9635 can be charged efficiently. When a lithium ion battery is used as thebattery9635, there is an advantage of downsizing or the like.

The structure and operation of the charge anddischarge control circuit9634 illustrated inFIG. 13B are described with reference to a block diagram ofFIG. 13C.FIG. 13C shows thesolar battery9633, thebattery9635, theDCDC converter9636, a converter9637, switches SW1 to SW3, and thedisplay portion9631. Thebattery9635, theDCDC converter9636, the converter9637, and the switches SW1 to SW3 correspond to the charge anddischarge control circuit9634 inFIG. 13B.

First, an example of operation in the case where power is generated by thesolar battery9633 using external light is described. The voltage of power generated by the solar cell is raised or lowered by theDCDC converter9636 so that a voltage for charging thebattery9635 is obtained. When thedisplay portion9631 is operated with the power from thesolar battery9633, the switch SW1 is turned on and the voltage of the power is raised or lowered by the converter9637 to a voltage needed for operating thedisplay portion9631. In addition, when display on thedisplay portion9631 is not performed, the switch SW1 is turned off and a switch SW2 is turned on so that charge of thebattery9635 may be performed.

Here, thesolar battery9633 is shown as an example of a power generation means: however, there is no particular limitation on a way of charging thebattery9635, and thebattery9635 may be charged with another power generation means such as a piezoelectric element or a thermoelectric conversion element (Peltier element). For example, thebattery9635 may be charged with a non-contact power transmission module that transmits and receives power wirelessly (without contact) to charge the battery or with a combination of other charging means.

It is needless to say that one embodiment of the present invention is not limited to the above-described electronic devices as long as the display device of one embodiment of the present invention is incorporated.

This embodiment can be implemented in an appropriate combination with any of the structures described in the other embodiments.

REFERENCE NUMERALS

101: flexible display panel,102-1: flexible substrate,102-2: flexible substrate,111-1: housing,111-2: frame member,112-1: housing,112-2: frame member,113-1: housing,113-2: frame member,121: battery unit,122: control unit,125: FPC,128: side frame member,130: wiring,132: opening,133: opening,134: wiring.1212: conductive layer,1271: p-type semiconductor layer.1273: i-type semiconductor layer,1275: n-type semiconductor layer,1280: conductive layer.600: main substrate,601: speaker.602: camera.603: display panel,604: battery unit,605: antenna for portable communication,606: antenna for NFC.611: quartz crystal unit,612: DRAM,613: application processor,614: baseband processor,615: electronic compass,616: quartz crystal unit,617: RF transceiver IC,618: touch panel control IC,619: acceleration sensor,620: module,621: power supply control IC,622: power amplifier for W-CDMA,623: flash memory,624: filter,1101: element layer,1103: substrate,1104: light extraction portion,1105: bonding layer,1106: driver circuit portion.1108: FPC,1108a: FPC,1108b: FPC.1156: conductive layer1157: conductive layer,1201: substrate,1202: substrate,1203: bonding layer,1205: insulating layer,1207: insulating layer,1208: conductive layer,1209: insulating layer,1209a: insulating layer,1209b: insulating layer,1211: insulating layer,1213: sealing layer;1215: connector,1215a: connector,1215b: connector,1217: insulating layer,1230: light-emitting element,1231: lower electrode,1233: EL layer,1235: upper electrode,1240: transistor,1255: insulating layer,1257: light-blocking layer,1259: coloring layer.1261: insulating layer,1270: conductive layer,1272: conductive layer,1274: conductive layer,1276: insulating layer,1278: insulating layer,1281: conductive layer.1283: conductive layer,1291: insulating layer,1292: conductive particle,1293: insulating layer,1294: conductive layer,1295: insulating layer,1296: conductive layer,1301: formation substrate,1303: separation layer,1305: formation substrate,1307: separation layer,1310a: conductive layer.1310b: conductive layer,9600: tablet terminal,9625: switch,9626: switch,9627: power switch,9628: operation switch,9629: fastener,9630: housing.9631: display portion,9632: region,9633: solar battery.9634: charge and discharge control circuit,9635: battery,9636: DCDC converter,9637: converter,9638: operation key,9639: hinge portion,9630a: housing,9630b: housing

This application is based on Japanese Patent Application serial no. 2013-179069 filed with Japan Patent Office on Aug. 30, 2013, the entire contents of which are hereby incorporated by reference.

Claims (15)

The invention claimed is:

1. A display device comprising:

a flexible display panel;

a first housing supporting a first portion of the flexible display panel;

a second housing supporting a second portion of the flexible display panel;

a first battery unit in the first housing;

a second battery unit in the second housing;

a control unit in the second housing, the control unit being configured to control the display device; and

a wiring,

wherein the first battery unit and the control unit are electrically connected with each other through the wiring,

wherein the flexible display panel comprises a bend portion between the first housing and the second housing, and the first housing and the second housing overlap with each other when the flexible display panel is folded, and

wherein the wiring is provided inside the flexible display panel or in contact with and along a surface of the flexible display panel.

2. The display device according toclaim 1, wherein the flexible display panel is an active matrix light-emitting device.

3. The display device according toclaim 1, wherein the flexible display panel is a liquid crystal display device.

4. The display device according toclaim 1, further comprising a flexible substrate between the flexible display panel and each of the first housing and the second housing.

5. The display device according toclaim 1, wherein at least one of the first battery unit and the second battery unit is charged with a non-contact power transmission module.

6. A display device comprising:

a flexible display panel;

a first housing supporting a first portion of the flexible display panel;

a second housing supporting a second portion of the flexible display panel;

a third housing supporting a third portion of the flexible display panel;

a first battery unit in the first housing;

a second battery unit in the second housing;

a circuit in the third housing; and

a wiring,

wherein the second portion is positioned between the first portion and the third portion,

wherein the flexible display panel is electrically connected to the circuit through the wiring,

wherein the flexible display panel comprises a first bend portion between the first housing and the second housing and a second bend portion between the second housing and the third housing,

wherein the first to third housings overlap with one another when the flexible display panel is folded by bending the first bend portion and the second bend portion, and

wherein the wiring is provided inside the flexible display panel or in contact with and along a surface of the flexible display panel.

7. The display device according toclaim 6, wherein the flexible display panel is an active matrix light-emitting device.

8. The display device according toclaim 6, wherein the flexible display panel is a liquid crystal display device.

9. The display device according toclaim 6, further comprising a flexible substrate between the flexible display panel and each of the first housing, the second housing, and the third housing.

10. The display device according toclaim 6, wherein at least one of the first battery unit and the second battery unit is charged with a non-contact power transmission module.

11. A display device comprising:

a flexible display panel;

a first housing supporting a first portion of the flexible display panel;

a second housing supporting a second portion of the flexible display panel;

a battery unit in the first housing;

a control unit in the second housing, the control unit configured to control the display device; and

a wiring,

wherein the battery unit and the control unit are electrically connected with each other through the wiring,

wherein the flexible display panel comprises a bend portion between the first housing and the second housing, and the first housing and the second housing overlap with each other when the flexible display panel is folded, and

wherein the wiring is provided inside the flexible display panel or in contact with and along a surface of the flexible display panel.

12. The display device according toclaim 11, wherein the flexible display panel is an active matrix light-emitting device.

13. The display device according toclaim 11, wherein the flexible display panel is a liquid crystal display device.

14. The display device according toclaim 11, further comprising a flexible substrate between the flexible display panel and each of the first housing and the second housing.

15. The display device according toclaim 11, wherein the battery unit is charged with a non-contact power transmission module.

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